JP3729995B2 - Calculation method of intake / exhaust valve open / close timing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an intake / exhaust valve opening / closing timing calculation method applied to control of an internal combustion engine having a variable valve timing mechanism.
[0002]
[Prior art]
Conventionally, as described in JP-A-5-156972, a variable valve timing capable of freely changing at least one of opening / closing timings of an exhaust valve and an intake valve with respect to a reference phase such as a crank angle reference signal This mechanism uses the variable valve timing mechanism to control the opening and closing timing so that it becomes an optimum value according to the operating conditions such as the intake pipe pressure and the engine speed, and the output and idle stability are controlled. An internal combustion engine that has been improved has been developed.
[0003]
By the way, the opening / closing timing is measured, for example, by measuring a time difference between a reference signal output every time the crankshaft is at a certain angle and a valve timing signal output from an opening / closing timing detecting means provided on the camshaft. It is obtained by calculating the phase difference of the valve timing signal with respect to the reference signal from the time difference and the engine speed at that time. The opening / closing timing is used as a parameter for various controls of the internal combustion engine, such as correction of fuel injection amount, intake pipe pressure, ignition timing, and the like.
[0004]
[Problems to be solved by the invention]
However, when the engine speed is low, such as immediately after the start of the internal combustion engine, particularly in an internal combustion engine with a small number of cylinders, the change in angular velocity within one rotation becomes large. If the phase obtained from the time difference between the signal and the valve timing signal and the engine speed is used, there is a problem that the error from the actual opening / closing timing is large and unstable. As a result, the fuel injection amount, the intake pipe pressure, or the ignition timing, etc., corrected using the opening / closing timing as a parameter become unstable and greatly different from the required value, and the air-fuel ratio becomes the target value. There was a risk that it would cause control failure of the internal combustion engine.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is configured to calculate the opening / closing timing from the control state of the variable valve timing mechanism at the time when the engine speed is low in an internal combustion engine having a variable valve timing mechanism. Therefore, the influence of the change in the angular speed of the engine rotation is eliminated from the calculated opening / closing timing, and the error from the true value is made small and stable.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
That is, the present invention Intake valve opening / closing timing It has a variable valve timing mechanism that can freely change the opening and closing timing. Correct as a parameter Internal combustion engine Other than the variable valve timing such as fuel injection amount, ignition timing, intake pipe pressure, etc. A calculation method of the opening / closing timing applied to control, comprising: An intake timing sensor that outputs an intake cam signal is provided on the intake camshaft, and normally the opening / closing timing is calculated based on the detected intake cam signal. When the engine speed is detected and the detected engine speed is below a predetermined speed, The variable valve timing mechanism is controlled to be at the most retarded position, and instead of the opening / closing timing calculated based on the intake cam signal, The opening and closing timing The value of the most retarded state that was previously learned and memorized It is characterized in that it is set to.
[0007]
By using such a calculation method, in the state where the engine speed is low and the angular speed change within the unit rotation is large, the influence of the angular speed change can be eliminated, and the opening / closing timing applied to the control can be calculated. The error between the calculated opening / closing timing and the true opening / closing timing can be made small and stable. Therefore, the fuel injection amount, the ignition timing, the intake pipe pressure, etc., which are corrected using the calculated opening / closing timing as a parameter, can be made stable so as not to greatly differ from the required values, and control failure of the internal combustion engine can be avoided.
[0008]
In addition, in order to make the error between the calculated opening / closing timing and the actual opening / closing timing small and stable during a predetermined time after the start of the start when the operation state of the internal combustion engine is unstable, An intake timing sensor that outputs an intake cam signal is provided on the intake camshaft, and normally the opening / closing timing is calculated based on the detected intake cam signal. The start time when the internal combustion engine starts rotating is detected, and for a predetermined time from the detected start time, The variable valve timing mechanism is controlled to be at the most retarded position, and instead of the opening / closing timing calculated based on the intake cam signal, The opening and closing timing The value of the most retarded state that was previously learned and memorized It is desirable to set to.
[0009]
【Example】
An embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 is a schematic diagram of an internal combustion engine 1 (only one cylinder is shown), to which the present invention is applied. The engine 1 is, for example, a three-cylinder for an automobile, and includes an intake system including a throttle valve 5, a surge tank 6, an intake pipe 7 and the like that are opened and closed in conjunction with an accelerator pedal (not shown), and in the vicinity of the end of the intake system. The fuel injection valve 8 is arranged to inject fuel, the cylinder 10 is provided with a combustion chamber 10a for burning the air-fuel mixture by ignition by a spark plug 9, and an exhaust system up to a muffler (not shown). Yes.
[0010]
The combustion chamber 10a is provided with an intake valve 2 and an exhaust valve 3 so as to open and close in synchronization with engine rotation by a cam mechanism. The valve operating mechanism for the intake and exhaust valves 2 and 3 will be described in detail. The intake and exhaust valves 2 and 3 include stems 2a and 3a extending upward, respectively, and valve springs (not shown) are provided above the stems 2a and 3a. The valve lifters 2b and 3b are assembled. Cams 13 and 14 formed on the intake camshaft 11 and the exhaust camshaft 12 are brought into contact with the valve lifters 2b and 3b, respectively. In this embodiment, as shown in FIGS. 2 and 3, a timing pulley 15 provided at one end of the exhaust camshaft 12 and a timing pulley (not shown) provided at one end of the crankshaft of the engine are connected to the timing belt. 16 are connected. As is well known, the gear ratio of these timing pulleys is set so that the exhaust camshaft 12 rotates once while the crankshaft rotates twice. The intake side camshaft 11 is connected to the exhaust side camshaft 12 via the variable valve timing mechanism 4 so that the opening / closing timing of the intake valve 2 can be made variable with respect to the opening / closing timing of the exhaust valve 3.
[0011]
The variable valve timing mechanism 4 uses a so-called oscillating cylinder mechanism, and is driven by hydraulic pressure. For example, as shown in FIGS. 3 to 5, a rotor 17 fixed to the exhaust camshaft 12 and an external fitting to the rotor are provided. A housing 18 that rotates, and an oil control valve 19 that rotates the housing 18 relative to the rotor 17 (hereinafter referred to as OCV), one of which is fixed to the housing 18 so as to mesh with each other, and the other is fixed to the intake camshaft 11. A pair of scissor gears 20, 21 is provided, and by changing the relative angle of the housing 18 with respect to the rotor 17, an arbitrary rotational phase difference can be generated between the exhaust side camshaft 12 and the intake side camshaft 11. It has a function that can be. As is well known, the gear ratio of the scissor gears 20 and 21 is set to be 1: 1 so that the rotational speeds of the intake side camshaft 11 and the exhaust side camshaft 12 are the same.
[0012]
Specifically, the rotor 17 has a cylindrical shape, and its inner side surface 17a is externally fitted and fixed to the exhaust-side camshaft 12, and, for example, four vanes 22 protrude from the outer side surface 17b in the radial direction. It is.
The housing 18 is a disc-shaped member having a through hole in the center, and is attached to the rotor 17 so that the through hole is fitted to the rotor 17 so as to be rotatable. Further, the housing 18 is fan-shaped when viewed from the front, and is provided symmetrically with respect to the four chambers 18a that open on the side surface of the through hole. When the housing 18 is externally fitted to the rotor 17 as described above, Each vane 22 is configured to partition each room 18a into two chambers 18a and 18c.
[0013]
As shown in FIG. 3, the OCV 19 is a so-called electromagnetic four-way spool valve having two input ports 19a and 19b and two output ports 19c and 19d, and the internal fluid path is switched by the advance and retreat of the spool 19e. The output ports 19c and 19d communicate with either the input port 19a or 19b, respectively. Further, in the neutral position of the spool 19e, the internal fluid path can be blocked so that the output ports 19c and 19d and the input ports 19a and 19b do not communicate with each other. FIG. 3 shows a state where the spool 19e is in the neutral position. The advance / retreat of the spool 19e is performed by an OCV drive signal a which is an electric pulse signal input from the outside, and the advance / retreat distance can be changed according to the on / off duty ratio of the OCV drive signal a.
[0014]
Next, a hydraulic path related to the variable valve timing mechanism 4 will be described. As shown in FIGS. 3 to 5, the output of the hydraulic pump P that is a power source of the variable valve timing mechanism 4 and is driven by the engine 1 is connected to one input port 19 a of the OCV 19. The other input port 19b is connected to the tank T. The output ports 19c and 19d of the OCV 19 are respectively connected to one end of two through holes 12a and 12b provided inside the exhaust side camshaft 12, and the other end of each through hole 12a and 12b is connected to the exhaust port. In the outer surface of the side camshaft 12, two grooves 12c and 12d provided in parallel along the circumferential direction are opened. These grooves 12c and 12d are provided in a portion where the rotor 17 is externally fitted. As shown in FIG. 4, the rotor 17 has one end opened to the other groove 12d and the other end partitioned by a vane 22. As shown in FIG. 5, the first fluid path 17c opens into the advanced chamber 18b, and one end opens into one groove 12c and the other end opens into the retard chamber 18c partitioned by the vane 22. Two fluid paths 17d.
[0015]
By configuring the hydraulic path in this way, the pump P is in the advance chamber 18b, the tank T is in communication with the retard chamber 18c, the first state, the pump P is in the retard chamber 18c, and the tank T is advanced. The second state in which the corner chamber 18b communicates and the third state in which the pump P and the tank T do not communicate with the retard chamber 18c and the advance chamber 18b are realized by moving the spool 19e of the OCV 19 forward and backward. . Therefore, by controlling the OCV 19 and maintaining the first state, oil is introduced into the advance chamber 18b to increase its capacity, and the vane 22 contacts the one end of the chamber 18a as shown in FIG. Can be rotated. This acts to shift the opening / closing timing of the intake valve 2 described later to the advance side. Further, by maintaining the second state, oil is introduced into the retarding chamber 18c to increase its capacity, and the vane 22 is rotated to the most retarded position where it abuts against the other end of the chamber 18a as shown in FIG. be able to. This acts to shift the opening / closing timing of the intake valve 2 to the retard side. Further, when the vane 22 is stopped in the meantime, it may be held in the third state. In this way, the vane 22 is rotated between the angle ranges θ shown in FIGS. 6 to 7 so that the relative angle of the housing 18 to the rotor 17 can be arbitrarily changed within the range of the angle θ.
[0016]
On the other hand, the intake camshaft 11 is interlocked with the housing 18 via the scissor gears 20 and 21, and the exhaust camshaft 12 is rotated integrally with the rotor 17. Therefore, as described above, the rotational phase difference between the intake camshaft 11 and the exhaust camshaft 12 can be arbitrarily set between the angles θ by changing the relative angle of the housing 18 to the rotor 17 within the range of the angle θ. Become. That is, the variable valve timing mechanism 4 according to the present embodiment changes the opening / closing timing of the intake valve 2 while always opening / closing the exhaust valve 3 with respect to the rotation of the crankshaft, while changing the opening / closing timing of the exhaust valve 3. And the opening / closing timing of the intake valve 2 can be freely changed between the angles θ.
[0017]
Furthermore, in this embodiment, as shown in FIG. 4, the pin 23 urged in the protruding direction by the spring 23a on the housing 18 is engaged with the hole 17e provided in the rotor 17 at the most retarded position. Provided. The opposite side of the hole 17e that engages with the pin 23 communicates with the groove 12d. When the hydraulic pressure is generated, the hydraulic pressure causes the pin 23 to immerse against the urging force of the spring 23a. The relative rotation is not prohibited.
[0018]
The electric control of the engine 1 having the above-described configuration is performed by the electronic control device 24. Next, in addition to the electronic control unit 24, main sensors, electrical wiring, and the like related to electrical control of the present embodiment will be described in detail below.
As main sensors according to this embodiment, for example, the following sensors are provided as shown in FIGS. In other words, the exhaust camshaft 12 is a pulse signal every time the crankshaft rotates 720 ° CA (hereinafter, when the phase of the crankshaft is described, the angle is represented by CA in this way). There is provided an exhaust side timing sensor 25 that outputs a cylinder discrimination signal c and outputs an exhaust cam signal b that is a pulse signal each time it rotates by 240 ° CA. The intake-side camshaft 11 is provided with an intake-side timing sensor 26 that outputs an intake cam signal d that is a pulse signal every rotation of 240 ° CA. In this embodiment, as shown in FIG. 2, for example, a total of 4 of the teeth for outputting the exhaust cam signal b arranged every 120 ° and one additional tooth for outputting the cylinder discrimination signal c provided elsewhere. A gear 25 a having teeth is attached to the timing pulley 15 of the exhaust side camshaft 12, and a pickup sensor disposed close to the gear 25 a is used as the exhaust side timing sensor 25. Similarly, the intake camshaft 11 is provided with a gear 26a having a total of three intake cam signal d teeth arranged every 120 °, and is arranged close to the gear 26a. This pickup sensor is used as the intake side timing sensor 26. In addition, a rotational speed sensor (not shown) that detects the engine rotational speed NE and outputs an engine rotational speed signal g, an idle switch 27 that outputs an idle switch signal IDSW when the throttle opening is in an idle state, and a throttle opening A power switch 28 that outputs a power switch signal PSW when the air pressure exceeds a certain value, or an intake pipe pressure sensor 29 that detects the intake pipe pressure PM and outputs an intake pipe pressure signal h is provided.
[0019]
As shown in FIG. 1, the electronic control device 24 is generally known as a so-called microcomputer device including a central processing unit 24a, a storage device 24b, an input interface 24c, an output interface 24d, and the like. Various programs for controlling the engine 1 and the like are stored in the storage device 24a. The input interface 24c receives at least an exhaust cam signal b, an intake cam signal d, a cylinder discrimination signal c, an idle switch signal IDSW, a power switch signal PSW, an intake pipe pressure signal h, an engine speed signal g, and the like. ing. The output interface 24d outputs at least an OCV drive signal a, which is a control signal for the variable valve timing mechanism 4, a drive signal f for the fuel injection valve 7, an ignition signal e for the spark plug, and the like.
[0020]
Of course, in addition to this, various members, sensors, and the like that are generally used in automobiles are constituent elements, but are omitted in this specification.
In this configuration, the present embodiment is characterized in that the calculation of the opening / closing timing VT applied to the control of the engine 1 is performed by the following method. That is, the output timing of the intake cam signal d0 when the vane 22 is in the most retarded position and the intake valve 2 is in the most retarded state is learned and stored in advance, and this is used as the reference phase. Normally, the phase difference between the detected intake cam signal d and the intake cam signal d0 in the most retarded state is set as the opening / closing timing VT. Therefore, when the engine speed NE falls below a predetermined speed, the opening / closing timing VT is set to 0 regardless of the detected phase difference value. That is, the electronic control unit 24 recognizes that the intake valve 2 is opened and closed in the most retarded state.
[0021]
Specifically, a subroutine showing this calculation method will be described with reference to a flowchart shown in FIG. 8 and a timing chart shown in FIG. In FIG. 9, for example, if the code is related to the first cylinder, (1) is added to the code, and the code for each cylinder is distinguished.
Steps S1 to S3 are routines for determining whether or not the detected engine speed NE is lower than the predetermined engine speed. In this embodiment, in order to prevent erroneous determination, a low predetermined engine speed NEL is set to a predetermined engine speed. (For example, 200 rpm) and a high predetermined rotational speed NEH (for example, 500 rpm) are provided to provide hysteresis.
[0022]
Specifically, in step S1, it is determined whether or not the engine speed NE is below a low predetermined speed NEL. If it is lower, the process proceeds to step S4, and if not, the process proceeds to step S2.
In step S2, it is determined whether or not the engine speed NE exceeds a high predetermined speed NEH. If so, the process proceeds to step S6, and if not, the process proceeds to step S3.
[0023]
In step S3, it is determined whether or not the value of the operation prohibition flag FLGVT0 set in steps S4 and S5 described later is 1. If the value is 1, the process proceeds to step S4. Otherwise, the process proceeds to step S6.
Steps S4 and S5 relate to a method of calculating the opening / closing timing VT when the detected engine speed NE falls below a predetermined speed. Specifically, in step S4, the value of the operation prohibition flag FLGVT0 is set to 1, and the process proceeds to step S5.
[0024]
In step S5, the opening / closing timing VT is set to 0, and the target opening / closing timing VTT is set to 0. Then, the process proceeds to step S8, and this subroutine in this time cycle is terminated.
Steps S6 and S7 are the same as in the conventional method for calculating the opening / closing timing VT. Specifically, in step S6, the value of the calculation prohibition flag FLGVT0 is set to 0, and the process proceeds to step S7.
[0025]
In step S7, the exhaust cam signal b and the intake cam signal d for each cylinder (for example, the first cylinder) are detected, and the intake air is determined from the time difference between the detected intake cam signal d and the exhaust cam signal b and the engine speed NE at that time. An actual phase difference VTB between the cam signal d and the exhaust cam signal b is calculated. Then, the difference between the most retarded learning value GVTFR, which is the phase difference between the intake cam signal d0 and the exhaust cam signal b in the most retarded state that has been learned and stored in advance, and the actual phase difference VTB is opened and closed. VT. Further, the target opening / closing timing VTT is set by a function f having the engine speed NE and the intake pipe pressure PM as parameters. Then, the process proceeds to step S8, and this subroutine in this time cycle is terminated.
[0026]
Although not shown, a correction subroutine for correcting the ignition timing, intake pipe pressure, fuel injection amount, etc. to be output using the calculated opening / closing timing VT after the completion of this subroutine within this time cycle, and this opening / closing timing. A first valve timing control subroutine for feedback control of the variable valve timing mechanism 4 so that VT becomes the target opening / closing timing VTT, or when the engine speed NE falls below the predetermined speed, the variable valve timing mechanism 4 is A second valve timing control subroutine is provided for controlling the vane 22 to the most retarded position and controlling the opening / closing timing of the intake valve 2 to the most retarded state.
[0027]
In addition, the variable valve timing mechanism 4 is controlled to the most retarded position shown in FIG. 7 when the operation of the engine 1 is finished, and the pin 23 is engaged with the hole 17e after the operation is finished. This is because the intake side camshaft 11 and the exhaust side camshaft 12 are mechanically connected to each other to open and close the intake valve 2 even when no hydraulic pressure is supplied to the variable valve timing mechanism 4 when the engine is started. This is because it is performed stably.
[0028]
According to the present embodiment configured as described above, when the engine speed NE is lower than the predetermined speed, the control by the second valve timing control subroutine described above is performed. Then, it is set to a value (0 in this embodiment) calculated from the control state of the variable valve timing mechanism 4 at that time, that is, the state where the vane 22 is in the most retarded position. Therefore, the engine speed NE and the intake cam signal d are not used for the calculation of the opening / closing timing VT, and the influence of the change in the angular speed of the engine rotation can be eliminated, thereby preventing the error from the actual opening / closing timing from becoming largely unstable. . As a result, the fuel injection amount, ignition timing, intake pipe pressure, etc., which are corrected using the opening / closing timing VT as a parameter in the above-described correction subroutine, can be made stable so as not to greatly differ from the required values. Control failures can be avoided.
[0029]
In addition, this invention is not limited only to the Example shown above. For example, in the embodiment, the opening / closing timing VT is set to 0 under the condition that the detected engine speed NE is lower than a predetermined predetermined speed, but this condition is maintained for a predetermined time from the start of the engine 1 start. It is good. In this case, steps S101 to S105 are applied instead of steps S1 to S3 as shown in FIG. This modification is based on the assumption that the engine 1 is applied to the same engine as in the embodiment, and the same members and control steps as those in the embodiment are denoted by the same reference numerals.
[0030]
Specifically, it is determined in step S101 whether the engine 1 has started. This may be performed by, for example, determining whether or not the engine speed NE is greater than 0, or determining whether or not it is after the time when the ignition key is at the start position. If it is determined that the engine has started, the process proceeds to step S102. If not, the process proceeds to step S105.
[0031]
In step S102, it is determined whether or not the time measurement variable TMCT is below a constant MXCT determined in correspondence with the predetermined time. If it is below, it is determined that it is within a predetermined time from the start of engine start, and the routine proceeds to step 103. Otherwise, it is determined that the predetermined time has elapsed, and the process proceeds to step S6 in FIG.
In step S103, 1 is added to the time measurement variable TMCT, and the process proceeds to step S4 in FIG.
[0032]
On the other hand, in step S104, since the engine 1 is not yet started, the variable TMCT is set to 0, and then the process proceeds to step S8 in FIG.
Thus, in this modification, the opening / closing timing VT is set to 0 when the engine speed NE is low immediately after the start of the engine and the operating state of the engine 1 is not stable. Therefore, as in the embodiment, it is possible to eliminate the influence of the change in the angular speed of the engine rotation on the calculation of the opening / closing timing VT, and to prevent the error from the actual opening / closing timing from becoming largely unstable. Note that the opening / closing timing VT is set to 0 because the control state of the variable valve timing mechanism 4 immediately after the start of the engine is started is that the intake side camshaft 11 and the exhaust side camshaft 12 are connected by the pin 23 as described above. This is because they are mechanically connected and the vane 22 is in the most retarded position.
[0033]
Needless to say, the present invention is applicable to an engine having a number of cylinders other than three.
In addition, the structure of each part is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.
[0034]
【The invention's effect】
As described above, the present invention Intake valve opening / closing timing It has a variable valve timing mechanism that can freely change the opening and closing timing. Correct as a parameter Internal combustion engine Other than the variable valve timing such as fuel injection amount, ignition timing, intake pipe pressure, etc. A calculation method of the opening / closing timing applied to control, comprising: An intake timing sensor that outputs an intake cam signal is provided on the intake camshaft, and normally the opening / closing timing is calculated based on the detected intake cam signal. Within a predetermined time from when the engine rotation is unstable and the engine starts slowly, The variable valve timing mechanism is controlled to be at the most retarded position, and instead of the opening / closing timing calculated based on the intake cam signal, The opening and closing timing The value of the most retarded state that was previously learned and memorized This is a method for calculating the opening / closing timing. Therefore, it is possible to eliminate the influence of the change in the angular speed of the engine rotation in the calculation of the opening / closing timing, and to prevent the error from the actual opening / closing timing from becoming largely unstable. As a result, the fuel injection amount, the ignition timing, the intake pipe pressure, etc., which are corrected using the opening / closing timing as a parameter, can be made stable so as not to greatly differ from the required values, and engine control failure can be avoided.
[Brief description of the drawings]
FIG. 1 is an overall schematic diagram showing an embodiment of the present invention.
FIG. 2 is a schematic view showing an intake / exhaust side camshaft portion of the embodiment.
FIG. 3 is a schematic sectional view mainly showing a variable valve timing mechanism of the embodiment.
4 is a partial sectional view taken along line AA in FIG. 3;
FIG. 5 is a partial cross-sectional view taken along line BB in FIG.
FIG. 6 is an operation explanatory diagram of a variable valve timing mechanism.
FIG. 7 is an operation explanatory diagram of a variable valve timing mechanism.
FIG. 8 is a flowchart showing a method for calculating the opening / closing timing of the intake valve in the embodiment.
FIG. 9 is a timing chart showing intake and exhaust cam signals in the embodiment.
FIG. 10 is a flowchart showing a part of an intake valve opening / closing timing calculation method according to a modification of the present invention.
[Explanation of symbols]
1 ... Internal combustion engine
2 ... Intake valve
3 Exhaust valve
4 ... Variable valve timing mechanism
VT ・ ・ ・ Opening / closing timing

Claims (2)

Control other than the variable valve timing, such as the fuel injection amount, ignition timing, intake pipe pressure, etc. of the internal combustion engine that has a variable valve timing mechanism that can freely change the opening / closing timing of the intake valve and uses this opening / closing timing as a parameter The above opening / closing timing calculation method is applied to the intake camshaft, and an intake timing sensor for outputting an intake cam signal is provided on the intake camshaft. Normally, the opening / closing timing is calculated based on the detected intake cam signal, and the engine speed When the detected engine speed is lower than a predetermined engine speed, the variable valve timing mechanism is controlled so as to be at the most retarded position, and is calculated based on the intake cam signal. instead of timing, is set to the value of the most retarded state close timing had previously been allowed to learning and memory Closing timing calculation method of intake and exhaust valves, characterized in that the. Control other than the variable valve timing, such as the fuel injection amount, ignition timing, intake pipe pressure, etc. of the internal combustion engine that has a variable valve timing mechanism that can freely change the opening / closing timing of the intake valve and uses this opening / closing timing as a parameter The opening / closing timing calculation method applied to the engine is provided with an intake timing sensor that outputs an intake cam signal to an intake camshaft, and normally calculates the opening / closing timing based on the detected intake cam signal. A start time at which the rotation starts is detected, and during a predetermined time from the detected start time, the variable valve timing mechanism is controlled to be at the most retarded position and is calculated based on the intake cam signal. instead of opening and closing timing, setting the value of the most retarded state close timing had previously been learned and stored Closing timing calculation method of intake and exhaust valves, characterized in that the so that.

Images